It is well known in the steel making art that the hearth of an iron blast furnace is provided with a tap hole, commonly referred to as an "iron notch" through which molten iron, usually referred to as "hot metal", is drawn off at periodic intervals during a blast furnace campaign. During a normal campaign, such tapping must be done on an average of five to twelve times daily as the blast furnace hearth becomes filled with molten iron and slag. After the blast furnace has been tapped; i.e., the molten hot metal and slag drained therefrom, the tap hole or iron notch is plugged with clay or "mud" which will harden in place to seal the tap hole until the next time the blast furnace is tapped.
In accordance with more conventional prior art practices, a special drill is utilized to open the tap hole; i. e., drill a passage way through the hardened clay plugging the iron notch for purposes of tapping the blast furnace through such the drilled hole. Such blast furnace tap hole drills are normally pneumatically or hydraulically operated rotary percussion drills comparable to the rock drills utilized in the mining industry. Such drills normally impart both a rotary and an impact force on an elongated drill rod having a rock drill bit at the end towards the iron notch.
More recently, some steel mills have converted to a "soaking bar practice" for tapping a blast furnace wherein, like the prior practice, a pliable, moist clay is used to plug the iron notch, but before the clay hardens completely, an elongated steel rod, referred to as a "soaking bar" is inserted through the pliable, moist clay plug so that the clay plug will harden around the steel soaking bar. The end of the soaking bar within the blast furnace hearth will naturally conduct a considerable amount of heat to the interior body of the clay plug, which not only hastened hardening of the clay plug, but tends to better cure the clay plug as an annular body around the soaking bar, so that when the blast furnace is ready to be tapped, the soaking bar can be pulled from the iron notch leaving a cleaner, more uniform, cylindrical aperture through the clay plug through which hot metal and slag can be tapped. The cleaner and better cured aperture will not only contribute to the ease and success of the hot metal flow therethrough during the tap, but the procedure eliminates many of the problems and costs previously encountered in the drilling of a tap hole.
The soaking bar is typically a cylindrical steel bar having a diameter of 1 to 2 inches, a length of from 10 to 15 feet, an end which is sharpened generally to a point (so that it can be driven into and through the clay plug), with the opposite end being threaded for purposes of attaching it to a coupling on the end of a two-directional pneumatic or hydraulic driving hammer so that it can be pulled from the clay plug. Like the prior art blast furnace tap hole drills, such driving hammers are usually pneumatically or hydraulically operated rotary percussion tools which impart both a rotary and an impact force on the outer end if the soaking bar to drive it into and through the unhardened clay. When a tap of the blast furnace is necessary, the same driving hammer is normally utilized by attaching it to the outer end of the soaking bar, and by utilizing the same rotary-impact force in the reverse direction, the soaking bar is withdrawn from the clay plug, which, as noted above, normally leaves a uniform, cylindrical aperture through the clay plug through which the blast furnace hot metal and slag are tapped. After tapping is completed, the iron notch is again plugged with pliable, moist clay and the procedure repeated for another heat of hot metal.
Since the prior art use of tap hole drills normally utilizes a rather large pneumatic or hydraulic drill which is interlinked to a base support such that the drill can be easily moved into and from a position for drilling the tap hole, this latter practice of utilizing a soaking bar has normally relied on the tap hole drill that is already present for the purposes of both inserting and removing the soaking bar into and from the clay plug plugging the blast furnace tap hole, as indeed the prior art drills are capable of imparting two-directional rotary, impact forces, not only as necessary to drill a tap hole, but also as necessary to insert and remove the soaking bars. Therefore, while the specific tapping practice may be changing, the equipment to be utilized in the soaking bar practice is not really different from the equipment utilized in the older tap hole drilling practice.
One thing that has not changed significantly, is the fact that which ever practice is utilized the effort to achieve a blast furnace tap is not a pleasant one. That is to say, the manual task of inserting and removing a soaking bar is still as unpleasant as the task of drilling a tap hole. Specifically, the tap crew must still work in a hot and hazardous environment adjacent to a hot blast furnace with interior temperatures well in excess of 3,000 F. Also, the atmosphere adjacent to a blast furnace is far from pleasant, as it usually contains noxious gases that manage to escape from the furnace. In addition, the site is always adjacent to the runner through which the blast furnace has previously been tapped. This runner, consisting of a fire-brick lined trough, usually built into the floor adjacent to the blast furnace, will usually retain an excessive amount of heat for a rather long period of time after the hot metal and slag have been tapped. Naturally any metallic component within the near vicinity of the tap hole, such as the drill, hammer, soaking bar plugging the tap hole, and the like, will be to hot to handle without protective gloves and additional protective clothing. Therefore, the tap crew is always anxious to prepare for a tap as quickly as possible in an effort to spend as little time as necessary in the rather unpleasant atmosphere in which they must work.
One practice that has become rather common in this effort to expedite the tap procedure, at least when using the soaking bar practice, is to use an old rag, or the like, wrapped around the soaking bar end to bind the outer end of the soaking bar into the coupling at the end of the rotary percussion tool. While this may reduce the amount of time necessary to connect the soaking bar to the coupling, it can and does often lead to later problems, such as the possibility that the soaking bar may not be well connected to the coupling, with the result that it may fall from the coupling during the effort the insert it into and through the clay plug. Should this result, the tapping time will of course be prolonged, as the hot soaking bar must be retrieved, reinserted into the coupling, and an attempt again made to insert it into and through the clay plug.